Method and apparatus for generating random signals

Abstract

A random binary signal is generated using a plurality of noise sources, each of which defines events occurring at random intervals, the outputs of the sources being combined in such a way that the events are interspersed in the resultant signal.

1. A method of generating a random binary waveform containing events which occur at random intervals, the method comprising:
 deriving, from a physical noise source, a first preliminary signal containing first events occurring asynchronously and at random intervals; and 
 multiplying the first preliminary signal with at least one further preliminary signal containing further events, said at least one further preliminary signal being a deterministic signal, so as to intersperse the first and further events; 
 wherein the physical noise source produces a non-deterministic output. 
 
   
   
     2. A method as claimed in  claim 1 , wherein the preliminary signals are combined by analogue multiplication. 
   
   
     3. A method as claimed in  claim 1 , wherein the preliminary signals are binary signals which are combined by binary multiplication. 
   
   
     4. A method as claimed in  claim 3 , wherein the preliminary signals are combined by an Exclusive-OR operation. 
   
   
     5. A method as claimed in  claim 1 , wherein said at least one further preliminary signal is a pseudo-random binary sequence. 
   
   
     6. A method as claimed in  claim 1 , wherein said at least one further preliminary signal is a chaotic signal. 
   
   
     7. A method as claimed in  claim 1 , including producing a signal form said physical noise source and applying a spectral filter to the signal in order to obtain said first preliminary signal. 
   
   
     8. A method as claimed in  claim 1 , wherein the number of preliminary signals, including said first and further preliminary signals, is equal to 3 or 4. 
   
   
     9. A method of detecting objects comprising measuring the delay between transmission of a signal modulated by a random binary waveform generated by a method according to  claim 1  and receipt of the reflection of the signal from the object. 
   
   
     10. Apparatus for generating a random binary waveform containing events which occur at random intervals, the apparatus comprising:
 a physical noise source producing a random output signal; 
 means for deriving, from said random output signal, a first preliminary signal containing first events occurring asynchronously at random intervals; 
 means for providing at least one further preliminary signal containing further events occurring at said random intervals, said further preliminary signal being a deterministic signal; and 
 means for multiplying the first preliminary signal and said at least one further preliminary signal so as to produce a random binary waveform in which said first and further events are interspersed; 
 wherein the physical noise source produces a non-deterministic output. 
 
   
   
     11. An apparatus as claimed in  claim 10 , wherein said at least one further preliminary signal is a pseudo-random binary sequence.